When exposing a mask and a wafer substrate in an adhesive position, there have been problems of causing patterning badness due to warpings of the mask or the wafer substrate or causing bad adherence therebetween due to a reaction gas, or problems of injuring the mask or the substrate due to dusts or bumps on their surfaces. For avoiding such problems, a proximity exposure method has been performed, which carries out replication of the mask pattern to the wafer substrate by closely approaching the former to the latter.
In a proximity exposure method, the mask makes fine displacements when the substrate is moved in a constant step. The displacement is generated by an atmospheric pressure change which occurs in a small clearance between the mask and the substrate, in particular when both come near or separate from each other.
If the mask pattern were replicated while the fine displacement remains in the mask, a transferring precision would be made inferior. Japan Patent Laid Open No.4-107911, as seen in FIG. 3, discloses a mechanism which opens a gas hole 60 in a support frame 41 outside a mask 40, and disposes a means for charging and discharging the atmoshpere with respect to the clearance between the mask 40 and a substrate 50, thereby to discharge the atmosphere between both when bringing the mask 40 nearer to the substrate 50, and on the other hand compulsively charge the atmosphere into the clearance to be pressurized when bringing farther. In addition, said publication shows a resistance generator 61 outside than the gas hole 60 of the frame supporter 41 in order to control an atmospheric currency with respect to an external for improving the atmospheric charging and discharging efficiency.
Depending upon the above stated mechanism, the approach and separation can be rapidly effected between the mask 40 and the substrate 50. However, said fine displacements of the mask are various by conditions of an atmosphere (an atmospheric air, He, etc.) between the mask 40 and the substrate 50, conditions of moving distances when approaching and separating, or those of deviations of relative center positions of the mask 40 and the substrate 50. And conditions of timing or speed of atmospheric pressure decompression or compression for controlling them are different respectively. In the above stated mechanism, however, when the mask 40 and the substrate 50 approach or separate, the controlling is deviated from the timings or speeds of the pressure decompression or compression suited to each time, because of a sequence control which is carried out for compulsive pressure decompression or compression at a predetermined (fixed) value by the controlling means, and so exact controlling of the atmospheric pressure is troublesome, and it is difficult to speed up the approaching and separating actions of the mask 40 and the substrate 50.